A 5 m aluminium wire (Y = 7 x 1010 N/m2) of diameter 3 mm supports a 40 kg mass. In order to have same elongation in a copper wire (Y = 12 x 1010 N/m2) of same length under same weight, the diameter should be, in mm :
(a) 2.0
(b) 2.3
(c) 1.75
(d) 5.0